Fluid electric heater



L. P. HYNES FLUID ELECTRIC HEATER Aprl 30, 1957 4 Sheets-Sheet FiledApril 26. JL956 INVENTOR Lee f m/ea April 30, 1957 L. P. HYNES FLUIDELECTRIC HEATER Filed April 26 1956 4 Sheets-Sheet 2 I qw?? April 30,1957' P HYNES 2,790,889

FLUID ELECTRIC HEATER Filed April ,26, 1956 4 Sheets-Sheet 3 INVENTORLee P Hyze B :sa

TTORNEY' April 30, 1957 P. HYNES FLUID ELECTRIC HEATER 4 Sheets-Sheet 4Filed April 26, 1956 INVENTOR zi. ee f ym BY g ATTO R N EYS UnitedStates Patent 2,790,889 Patented Apr. 30, 1957 FLUID ELECTRIC HEATER LeeP. Hynes, Haddofield, N. J., assignor to Turbina Equipment Company, NewYork, N. Y a corporation of New Jersey i Application April 26, 1956,Serial No. 580,870

11 Claims. (Cl. 219-39) The present invention relates to electricheate's for fiuids, especially gases, including air.

The purpose of the invention is to provide an electric heater for gaseshaving high energy input, with long service life and low maintenance.

A further purpose is to make an electric heater for gases more compact,and suitable for utilization in pressure vessels at small diameters, andin high temperature service.

A further purpose is to provide a plurality of resistor ribbons ofdeformed cross section (such as U-shaped cross section) extending inspaced side-by-side relation through a housing, with nsulator meanssupporting the ribbons -laterally and electrical cross connectionsbetween the ribbons, suitably between alternate ribbons at oppositeends.

A further purpose is to make the resistor ribbons resilient andinherently of a structural form which will support themselves, such as aU, and to permit lateral exing under expansion and contraction.

'A further purpose is to distribute the resistor ribbonscircumferentially around an axis, desirably in a circular cluster.

A further purpose is to place a gear-like insulator at the inside of thecluster engaging the radially interior edges of the resistor ribbons,and to place insulator clips engaging the radially exterior edges of theresistor ribbons, desirably surrounding the insulato' clips by bands.

A further purpose is to direct -the arms of the U's of the resistorribbons radially outwardly.

A further purpose is to extend a support rod through the interior of theresistor ribbons and the gear-like insulators, supporting the nsulatorsfrom the rod.

A further purpose is to insulate the support rod from the resistorribbons by a collar at the end. v

A further purpose is to provide lugs on the resistor ribbons whichposition the insulator clips.

A further purpose is to cross brace resistor -ribbons between thearms'of the U's.

A further purpose is to permit the fluid being heated to wash both theinsides and the outsides of the walls of the resistor ribbons. i

A further purpose is to mount a plurality of clusters of resistorribbons in spaced side-by-side relation in a housing, desirablyproviding jackets around the clusters, and to pass the fluid to beheated through the clusters inside the jackets.

A further purpose is to provide headers within the housing supportingthe jackets at the ends and a'bracket supporting one of the headers fromthe housing.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a 'few only of the numerousembodiments in which my invention may appear, selecting the forms shownfrom the standpoints of convenience in illustration, satisfactoryoperation and clear demonstration of theprinciples involved.

Figure 1 is a fragmentary axial ,section of an electric heater inaccordance with the invention, omitting the heads at the ends.

Figure 2 is a plan view of the heater of Figure 1, omitting the topheader.

Figure 3 is a fragmentary side elevation of the heating elements shownin Figures 1 and 2 omitting the housing and the insulator clips.

`Figure Sa is an enlarged fragmentary view similar to Figure 3 showingan alternate form.

Figure 4 is an enlarged end elevation of the electric heater' of Figures1 to 3 showing only the housing and the heater assembly, and omittingthe header.

Figure 5 is an enlarged fragmentary section of Figure l on the line 5-5.

Figure 6 is a fragmentary axial section of a modified embodiment of theinvention, the section being taken on the line 6-6 of Figur-e 7.

Figure 7 is a section on the line 7-7 of Figure 6.

Figure 8 is an enlarged section on the line 8-8 of Figura 6.

Describing in illustration but not in limitation and referring to thedrawings:

The present invention is concerned with electric heaters for fluids,which may permissibly be liquids, but in most cases are likely to begases. When reference is made herein to gas or gases, it is intended toinclude air, and one of the advantageous uses of the present inventionis to heat air for testing guided missiles, jet engines, and for use inwind tunnels and the like.

The invention is also applicable for heating gases utilized for examplein the Chemical industry. One example is heating of hydrogen andnitrogen which are being passed over a catalyst suitably at severalthousand p. s. i. and at elevated temperatures which may be as high as1700 F. or more, in order to make ammonia. Many of the installations inwhich the equipment of the invention will be applied are characterizedby high temperature alone, or high pressure alone, or both hightemperature and high pressure.

The invention is applicable also to installations embodying intermediateand low pressure and also to those in which moderate pressure ortemperature is emplayed.

One of the serious problems which has existed in the prior art is thatheating of fluids such as gases has been required in relatively smallspaces. Because of the expense of producng pressure vessels, it isfrequently desirable to use vessels of relatively small diameter whichleave little space -for installation of heaters. In many suchinstallations however the gas velocity is high and the gas Volume large,so that the heater cannot be Satisfactorily used if it seriouslyobstructs flow of the medium being heated. The high velocity of flowalso requires a relatively strong structure capable of sustaining theheater shape.

Many of the prior art heater designs have used small units which involveheating coils or the like with numerous electrical connections betweenheating units. While these units are very useful in many types ofservice, they are not adequate to meet the requirements in some of thenew Chemical processes and in some of the new testing installations.

The problem is further complicated by the fact that in some processesthe heating requirement is highly intermittent. The process for examplemay be exothermic and the heater in that case will be required merely toheat the reaction mixture up to the reaction temperature when theequipment is first placed on stream." The heater therefore must remaininactive for long periods of time in a relatively inaccessible positionwhere it is not open to frequent inspection, and yet must functionreliably whenever it is turned on. If the heater fails to aromes:)

3 function the expense is high in terms of idle equipment, for anyshut-down of the installation.

In a typical installation, used in producing annonia from hydrogen andnitrogen by a catalytic process, the internal diameter of the pressurevessel in which the bcater is required to function is only three inchesand the vesscl is thirty feet long. A very high density electric heaterwas previously installed, which burned out and required replacementafter every few hours of service. The prob lem was complicated byhydrogen embrittlcnent ol' the steel rods formerly used as resistors.

I have discovered an improved electric heatcr which is very suitable forinstallations of the type under discussion which, when installed in theammonia plant above referred to, has operated successfully withoutinterrupticn for several months.

In accordance With the invention the heating unit consists of a seriesof deformed resistor ribbons extending longitudinally in spacedside-by-side relationship. This has the advantage that the ribbons,being rcsilient, can readjust under expansion and contraction, the gasbeing heated can v ash against a large heating surface and preferablyagainst both su'faces of each ribbon, the heater is capable of servicein restricted diameters, and yet a minimum of interference with gas flowis provided. Thus there is a very high surface, and a mechanicallystrong structure which will withstand high velocity of dense gas at highpressure without mechanical or electrical failure.

Considering now the drawings in dctail but not in limitation, in theform of Figures 1 to 5 a tubular housing 20, which may be disposedvertically or horizontally as desired, is provided with heads at theends (not shown.) closing the entire structure into a pressurc vessel.The heads have suitably inlet and outlet connections (not shown), theinstallation normally inserting the medium at one end and withdrawing itat another end after passing longitudinally through the heater and insome cases through a Catalyst or Chemical reaction zone (not shown).

Inside the housing and extending longitudinally I provide a heater unit21 suitably in the form of a circular or circumferential cluster ofresistor ribbons 22 which in the form shown are desirably U-shaped, andwhich cxtend longitudinally from one end to the other of the heater.Each resistor ribbon comprises a base U bend 23 and generally radiallyextending u sides 24. The resistor ribbon is desirably of anelectrically resistor alloy such as nichrome, although any othersuitable resistor alloy may be employed.

At intervals along the heater unit gear-like insulators 25 of porcelainor the like are distributed at the center of the cluster, each of theseinsulators having a longitudinal recess 26 which receives the reversebend of the U at the inside of each resistor ribbon, and between eachpair of recesses 26 the insulator has a knob or rib 27 which spaces theinside loops of the resistor ribbons.

Each of the gear-like insulators 25 has a central opening 28 which'eceives and is supported on a central rod or tube 30 connected with thehousing in any suitable manner as later described. The number ofgear-like insulators 25 will be adjusted to fit the requirements of theparticular installation, although in many cases it will be suflicient tohave such insulators only at the opposite ends.

The gear-like insulator at the upper end in Figure l is shown supportedagainst longitudinal motion by washers 31 and 32 which are positioned onthe rod 30 by cotter pins 33 passing through holes in the rod. At thebottom an insulating collar 34 of porcelain or the like is provided,which extends out beyond the inside of the recesses in the gear-likeinsulator and engages to support the lower ends of the resistor ribbons,the collar surrounding the rod 30, and the collar and also the gear-likeinsulator beng supported as a unit by a Washer 35 on the top and alarger Washer 36 on the bottom, the washers being positioned by cottcrpins 37 passing through openings in the rod 30.

As best seen in Figures 4 and 5, the resistor ribbons extond radiallyoutwardly, and at suitable intervals individual arms of the ribbons arestraddled by insulator cti ?i? suitably of porcelain or the like similarto the gear-like insulators, having slots 40 which receive the cdgcs ofthe arms of the ribbons. Eachof the insulator clips has at its outeredge a recess 41 which receives a band 32 suitably of heat resistingmetallic alloy which ex tends around all of the clips at the particularposition and holds them in their placement. The bands are joined as byspot wetding.

The clips are prevented from slipping in either direction along theresistor ribbons by metallic lugs 43 which are weldcd or formed on theresistor ribbons longitudinally on. opposite sidcs of the clips asshown.

In order to provide suflicient torsional strength of the re istorribbons, it is desirable as an alternate to provide cross connection atthe outer ends of the arms of the U of the resistor ribbons by jumpersor bridgcs 44 weldcd to the insulator ribbons and illustrated in Figure3a ?The bridges are remote from the insulator clips.

The rod or tube 30 is desirably supported in any suitable manne', as by`extending cross bars 45 in spaced relation across the interior of thehousing near the upper end and providing key 46 which passes through anopening in the rod or tube and rests on the cross bars. To brace theheater unit in either direction against the housing, radial ribs 47 areprovided suitably at angular positions around the rod or tube 30 andextending to a position adjacent to the housing walls.

;in the form shown the lower end of the rod or tube 30 ,tloats to permitexpansion and contraction, and is guidcd by cross bars 48 extendingacross the interior of the housing below the heater unit.

It will be evident that the heater unit can be moved in or out of thehousing longitudinally by removing the cross bars 48, detaching theelectrical connections, and rotatin the heater until the key 46 willpass down through the space between cross bars 45.

The clectrical connections are Conveniently made through leads 50extending through diagranmatically illustrated pressure tube insulators51 in the housing wall. The leads at the inside engage flexibleconnecting straps 52 and are secured thereto by nuts 53 which holdtogether the pressurc tube insulators. The straps are suitably Welded tothe end of appropriate resistor ribbons as shown at 54 in Figura 4.

Current is arranged to pass in series through the entire cluster ofresistor ribbons, and for this purpose electrical jumpers 55 are weldedto adjoining arms of every alternate pair of resistor ribbons at one endof the heater and jumpers 56 are welded to the adjoining arms ot' .everyintervening pair of resistor ribbons at the opposite end of the heater,thus providing for current flow in Zig-Zag relationship (series).

It Will be understood that the device provides resistors of accordionformation which have great strength against torsion, but which aresufficiently resilient to lex laterally as required by expansion andcontraction.

It Will be evident that the insulator clips protect against thepossibilty that the resistor ribbons could touch the housing even ifthey were to be displaced under some c0udition of pressure or gas flow.

It will be evident that in case the unit is placed horizontally ratherthan being disposed vertically it may be desirable to distribute ringsof insulator clips at more fre quent intervls to bear the latcralComponent of the load and prevent sagging.

In some cases it is desirable to increase the Capacity of the units byplacng several clusters in arallel. A typical example of this isinpreheating air foitcst purposes.

A construction of this `kind is shown in Figures 6, 7 and 8 where threeheater clusters 21 are mounted to similar straps 57 and 58 at the ends.The heater clusters are surrounded in spaced relation by jackets 60which are connected at the ends as by welding to headers 61 and 62 whichengage but float freely longitudinally in the housing so as to adjustfor expansion and contraction. The straps 57 and 58 are Secured to therespective headers 61 and 62. The headers have holes at the endssubstantially as large as the jackets in line with the jackets.

The jackets avoid difiiculty through excessive radiation of the heatersof one cluster against an adjoining cluster.

In order to permit the medium entering at inlet 63 and leaving at outlet64 near the opposite ends to flow around the outside of the jackets aswell as through the interiors of the jackets, holes 65 are provided inthe headers outside the jackets, and the jackets function as efcientradiating surfaces since they are washed by the gas both inside andoutside. The openings in the ends of the headers are of the diameter ofthe jackets and are unobstructed except for the straps 57 and 58 whichwill suitably be of spider or skeleton Construction.

One of the headers 61 and the adjoining support element 57 are supportedby brackets 66 from a removable head 67 on the housing, the head beingflanged on the housing at 68 and suitably Secured as by welding or byattachments as desired. Suitable insulating leads 70, 71 and 72 are ledthrough the head 67 and extend to the heaters by wiring (not shown).Where these are threephase leads the heaters can be delta or starconnected as desred.

The jackets 60 have the advantage of absorbing heat by radiation andconveying the heat to the gas over a large area. It will be understoodthat the jackets need not be pressure tight as they are subjected to thesame pressure on the inside as well as on the outside.

In View of my invention and disclosure, variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of myinvention without copying the structure shown, and I, therefore, claimall such insofar as they fall within the reasonable spirit and scope ofmy claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a fluid heater, a housing, and a self-contained resstor unitwithin the housing comprising a longitudinal support in spaced relationfrom the housing, internal insulators Secured to the support atlongitudinally spaced points and having resistor receiving recessesdistributed around the insulators, resistors extending longitudinally,

postioned around the support in the space between the support and thehousing and engaging in the recesses in the internal insulators,external insulators engaging the outer edges of the resistors atlongitudinally spaced positions along the resistors, and adjacent theinterior of the housing, restraining bands extending around each groupof external insulators and holding the same in place, a longitudinallimiting insulator connected to the support and engaging one end of theresistors, the resistors being free to expand and contract at the endremote from said longitudinal limiting insulator, and electricalconnections to the resistors at the end adjacent the longitudinallimiting insulator.

2. A fluid heater of claim 1, in which the resistors conprise resliertribbons which are free to flex under expansion and contraction.

3. A fluid heater of claim 1, in which the internal insulators 'tre ofgear-like shape engaging radial interior edges or" the resistors, andthe resistors having edges expcsed at the outside, the externalinsulators engaging such radially extending exterior edges of theresistors.

4. A fluid heater of claim 1, in which the resistors are ribbons ofsubstantially U shape cross section.

S. A fluid heater of claim 4, in which the ribbons have the arms of theU directed radially outwardly.

6. A fluid heater ot' claim 1, in which the longitudinal limitinginsulator is a collar surrounding the support and extending outwardtherefrom.

7. A fluid heater of claim 1, in which the resistors are ribbons, incombination with lugs on the ribbons engaging the external insulatorsand limiting them against longitudina motion.

8. A fluid heater of claim 4, in combination with cross braces betweenthe arms of the U's.

9. A fluid heater of claim l, in combination with means for directngfluid flow to wash both the insides and the outsides of the resistors.

10. A fluid heater of claim 1, having a plurality of self-containedunits surrounded by individual jackets, a casing surrounding all of thejackets, means for supporting the units and the jackets inside thecasing and means for distributing the flow in predetermined proportionthrough the jackets and through the area surrounding the jackets.

11. A fluid heater of claim l, in combination with connections atalternate ends between adjacent resistors connecting a plurality of theresistors of a cluster into one series electrical circuit.

References Cited in the file of this patent UNITED STATES PATENTS

